Continuous annealing equipment, continuous annealing method, method of producing cold-rolled steel sheets and method of producing coated or plated steel sheets

Abstract

To provide continuous annealing equipment, a continuous annealing method, a method of producing cold-rolled steel sheets and a method of producing coated or plated steel sheets which enable a quick response to fluctuations in material properties and enable minimization of fluctuations in mechanical properties of products. The continuous annealing equipment is continuous annealing equipment for steel sheets including, in this order, a heating zone ( 6 ) and a soaking zone ( 7 ), the soaking zone ( 7 ) including a first soaking zone ( 7 A) and a second soaking zone ( 7 B) provided after the first soaking zone ( 7 A), the continuous annealing equipment including: a first induction heating device ( 9 ) provided between first soaking zone ( 7 A) and a second soaking zone ( 7 B); and a measuring device ( 10 ) configured to measure austenite fractions of the steel sheets at an exit of the second soaking zone ( 7 B).

1 . Continuous annealing equipment for steel sheets comprising a heating zone and a soaking zone in order of the heating zone and the soaking zone,
 the soaking zone including a first soaking zone and a second soaking zone provided after the first soaking zone,   the continuous annealing equipment comprising:   a first induction heating device provided between the first soaking zone and the second soaking zone; and   a measuring device configured to measure austenite fractions of the steel sheets at an exit of the second soaking zone.   
     
     
         2 . The continuous annealing equipment according to  claim 1 , further comprising a second induction heating device at the exit of the second soaking zone and before the measuring device. 
     
     
         3 . The continuous annealing equipment according to  claim 1 , further comprising a hot dip galvanizing bath following the continuous annealing equipment for steel sheets comprising the heating zone and the soaking zone the in the order of the heating zone and the soaking zone. 
     
     
         4 . A continuous annealing method performed with continuous annealing equipment for steel sheets comprising a heating zone and a soaking zone in order of the heating zone and the soaking zone,
 the soaking zone including a first soaking zone and a second soaking zone provided after the first soaking zone,   the continuous annealing equipment comprising: a first induction heating device provided between the first soaking zone and the second soaking zone; and a measuring device configured to measure austenite fractions of the steel sheets at an exit of the second soaking zone,   wherein the continuous annealing method comprises a step of adjusting an output of the first induction heating device and adjusting a furnace temperature of the second soaking zone based on the austenite fractions of the steel sheets measured by the measuring device.   
     
     
         5 . The continuous annealing method according to  claim 4 , wherein the step of adjusting the output of the first induction heating device and adjusting the furnace temperature of the second soaking zone uses a transformation rate control model constructed for each product. 
     
     
         6 . A continuous annealing method performed with continuous annealing equipment for steel sheets comprising a heating zone and a soaking zone in order of the heating zone and the soaking zone,
 the soaking zone including a first soaking zone and a second soaking zone provided after the first soaking zone,   the continuous annealing equipment comprising: a first induction heating device provided between the first soaking zone and the second soaking zone; and a measuring device configured to measure austenite fractions of the steel sheets at an exit of the second soaking zone,   wherein the continuous annealing method comprises a step of heating the steel sheets in the heating zone so that a temperature of each of the steel sheets increases in a temperature range lower than an A 1  transformation temperature,   a step of maintaining the temperature of each of the steel sheets in a temperature range lower than the A 1  transformation temperature at the first soaking zone,   the step of heating in the first induction heating device by 10° C./s or more and 200° C./s or less such that the temperature of each of the steel sheets is included in a temperature range of the A 1  transformation temperature or more and less than an A 3  transformation temperature, and   a step of maintaining the temperature of each of the steel sheets in the second soaking zone in a temperature range of the A 1  transformation temperature or more and less than the A 3  transformation temperature.   
     
     
         7 . A method of producing cold-rolled steel sheets, wherein the continuous annealing method according to  claim 4  anneals the steel sheets which are cold-rolled steel sheets. 
     
     
         8 . A method of producing coated or plated steel sheets, wherein a coating or plating treatment is applied to surfaces of the steel sheets annealed by the method of producing cold-rolled steel sheets according to  claim 7 , and
 the coating or plating treatment is electrogalvanizing, hot dip galvanizing treatment, or galvannealing.